عنوان مقاله [English]
Graphene sheets, the two-dimensional carbon nanostructures, amazingly exhibit electrical, mechanical, thermal, and optical properties so that they can be considered as a promising material for a wide range of applications such as composites, chemical sensors, ultra capacitors, transparent electrodes, photovoltaic cells, bio-devices and gigahertz oscillators. Although there have been numerous studies carried out on the simulation of vibrational behavior of perfect graphene sheets, notable studies representing the effects of nanopores on linear and/or nonlinear vibration responses of graphene sheets do not exist, while the existence of nanopores in graphene lattice can be essential based on the desired functionality of graphene sheets in different nano-devices. Therefore, the simulation of dynamic response of graphene sheets with nanopores to determine how the size, the position and the shape of cut-outs influence the natural frequencies is important. On the other hand, previous researches show that graphene vacancies can be used as anchoring points for nanoparticles or some molecules. Then, graphene nano-resonator sensors with designed vacancy defects may perform better than perfect ones because of the designed location of external mass instead of a randomly location. Therefore, the investigation of the impact of vacancy defects on natural frequencies of graphene sheets is the main objective of this article. The influence of different vacancy defects on the shift in the resonant frequency of grapheme nano-resonators is studied as well.Results clearly show that pinhole vacancies can decrease or increase the natural frequencies of graphene sheets depending on ratio of the hole diameter to the side length and chirality. The fundamental natural frequency of a graphene sheet with a big vacancy defect is higher than that of a sheet with several small vacancy defects when both lose the same number of atoms. It is also seen that the effect of nanopore on the natural frequencies decreases when a nanopore becomes closer to the supported edges. It also seems that zigzag graphene is more sensitive to the attached external mass compared to armchair graphene.